Generators in the power station field exhibit oscillations at double the line frequency in the region of the end-windings, inter alia. Damage to the insulation or, as the case may be, to the copper can occur at excessively high amplitudes of the bar oscillations. The damage can result in the destruction of the generator. Since the end-windings are at high-voltage potential, fiber-optic acceleration sensors (so-called FOAs=Fiber Optic Accelerometers) are increasingly used for monitoring such oscillations. An example of such an FOA operates with a centrifugal mass which is connected to an optical fiber and which is deflected by the occurring acceleration. The deflection can be transferred for example to a fiber Bragg grating (FBG), which is stretched as a result. A known method is also to convert the deflection of the centrifugal mass into a change in intensity of a light signal.